Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/68—Halogens or halogen compounds
  • B01D53/70—Organic halogen compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/38—Separation; Purification; Stabilisation; Use of additives
  • C07C17/389—Separation; Purification; Stabilisation; Use of additives by adsorption on solids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/102—Carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/116—Molecular sieves other than zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/30—Physical properties of adsorbents
  • B01D2253/302—Dimensions
  • B01D2253/308—Pore size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/20—Halogens or halogen compounds
  • B01D2257/206—Organic halogen compounds
  • B01D2257/2066—Fluorine
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Definitions

• HFOs hydrofluoroolefins
• Trans HFO-1234ze (trans-1,3,3,3-tetrafluoropropene) is one such material. Its global warming potential will meet all currently proposed guidelines. However, some fluoroolefins are known to be toxic or otherwise undesirable. Trans HFO-1234ze has been tested for toxicity and found to be generally non-toxic and very suitable for use as a blowing agent, refrigerant or solvent. Accordingly, the presence of other fluoroolefins, even at low concentrations, may be a cause for concern unless they have been tested for toxicity.
• HFO-1234 impurity a compound of HFO-1234 (C 3 H 2 F 4 ), such as HFO-1234zc, whose toxicity is unknown.
• HFO-1234zc a compound of HFO-1234
• a molecular sieve is a material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids. Molecules small enough to pass through the pores are adsorbed while larger molecules are not.
• the principle of absorption to molecular sieve particles is somewhat similar to that of size exclusion chromatography, except that without a changing solution composition, the adsorbed product remains trapped because in the absence of other molecules able to penetrate the pore and fill the space, a vacuum would be created by desorption.
• molecular sieves consist of aluminosilicate minerals, clays, porous glasses, microporous charcoals, zeolites, active carbons, or synthetic compounds that have open structures through which small molecules can diffuse.
• Another feature that can control the separation process is the kinetics of the materials to be separated.
• Foley at al., in U.S. Pat. No. 5,261,948, teach that oxygen and nitrogen differ in size by only 0.2 angstrom and the equilibrium loading levels of the two gases are almost identical. Nevertheless, their separation using carbon molecular sieves is efficient. This separation depends on the fact that the rate of transport of oxygen into the carbon sieve pore structure is much higher than that of nitrogen.
• Another factor that can affect the separation is the shape of gas molecules as compared to the shape of the opening in the adsorbent. The choice of molecular sieve as an adsorbent is therefore unobvious.
• the sieving material can be either a zeolite type or a carbon molecular sieve.
• Methods for the regeneration of molecular sieves include pressure change, heating and purging with a carrier gas, or heating under vacuum conditions. Temperatures typically used to regenerate water-adsorbed molecular sieves typically range from 130° C. to 250° C.
• molecular sieves of an acceptable effective pore size provides a process for separating trans HFO-1234ze from its mixture with other materials, particularly impurities which comprise the HFO-1234 impurity, whose molecular sieve diameters permit adsorption so as to reduce the amount of impurities in the mixture.
• the process may be conducted with any suitable molecular sieve and is suitable for separating trans HFO-1234ze from its mixture with any other material that has a molecular diameter, polarity, kinetics, shape, or other property such that a separation is possible.
• the process of this invention is particularly suitable for removing the HFO-1234 impurity from the desired compound, trans HFO-1234ze.
• This process may be conducted at a temperature of from about ⁇ 20° C. to 100° C. and comprises adsorbing the impurity by contacting the product stream with a solid adsorbent comprising pores having openings which have a size across their largest dimension in the range of from about 5 angstroms to about 10 angstroms.
• One preferred embodiment of this invention is thus directed to a process for removing impurities from a product stream comprising trans HFO-1234ze and an HFO-1234 impurity that uses one or more adsorbents that are selective for the HFO-1234 impurity, such that the HFO-1234 impurity is removed from the product stream.
• the process of the present invention is particularly suitable for removing the HFO-1234 impurity produced during the production of trans HFO-1234ze by interaction between the reaction products with a suitable adsorbent agent or combinations of such agents.
• the process may be conducted with any suitable molecular sieve that is suitable for separating the HFO-1234 impurity from a mixture with trans HFO-1234ze.
• the present invention is directed to a process for removing impurities from a product stream comprising trans HFO-1234ze and an HFO-1234 impurity that uses one or more adsorbents that are selective for the HFO-1234 impurity, such that the HFO-1234 impurity is removed from the product stream.
• One such impurity is HFO-1234zc, which is removed from its mixture with trans HFO-1234ze by action of an adsorbent having pores in the range of from about 5 angstroms to about 10 angstroms.
• the present inventors have found that the HFO-1234 impurity can be separated from trans HFO-1234ze by the use of molecular sieves whose pore diameters range from about 5 angstroms to about 10 angstroms.
• the preferred molecular sieves have a pore diameter of about 5 angstroms.
• a product stream containing the HFO-1234 impurity in a mixture with trans HFO-1234ze can be brought into contact with the molecular sieve in either the liquid or gas phase, in a process that may be either a continuous or a batch process to adsorb the HFO-1234 impurity and thereby separate and remove it from the trans HFO-1234ze.
• the level to which the HFO-1234 impurity is reduced is dependent upon the capacity of the molecular sieve and the equilibrium between the HFO-1234 impurity and the mixture of gases and in the molecular sieve itself. It is preferred to use as much molecular sieve as necessary to reduce the level of HFO-1234 impurity to less than about 500 ppm, preferably to level of less than about 100 ppm, and more preferably to a level of less than about 10 ppm. Most preferably, the level of the HFO-1234 impurity is undetectable, i.e., as close to “zero ppm” as possible.
• the process of this invention may employ any suitable molecular sieve including, but not limited to, suitable zeolite and carbon molecular sieves.
• the suitable molecular sieve must have an acceptable effective pore size such as to adsorb the HFO-1234 impurity but not adsorb the trans HFO-1234ze.
• 5 A molecular sieves (having an effective pore size of about 5 angstroms) will very effectively achieve the desired separation of HFO-1234 impurity from trans HFO-1234ze.
• the HFO-1234 impurity has an effective molecular diameter of less than about 5 ⁇ and that the effective molecular diameter of trans HFO-1234ze is greater than 5 angstroms.
• separation of the HFO-1234 impurity from trans HFO-1234ze can be effected by using molecular sieves whose diameters are less than the effective molecular diameter of trans HFO-1234ze.
• Molecular sieves useful in the process of this invention are available from a variety of sources, including but not limited to, zeolite molecular sieves from Universal Oil Products (UOP), Grace Chemical and Aldrich Chemical Co., and carbon molecular sieves from Aldrich Chemical Co., Chemos GmbH of Germany and Dayung Chemical Co., Ltd. of China.
• the present invention is illustrated by, but not limited to, the following examples.
• the present inventors compared the separation of the HFO-1234 impurity from a mixture with trans HFO-1234ze using two different molecular sieves, namely 13X sieves and 5A sieves (obtained commercially from UOP and Grace Chemical).
• the rough size of the pores in these sieves is about 10 angstroms and about 5 angstroms, respectively.
• the 13X sieve reduced the level of the HFO-1234 impurity somewhat, but did not remove it entirely.
• the 5A sieve was surprisingly effective in removing all of the HFO-1234 impurity. Table 1 below presents the data from the experiments conducted.
• the initial concentration of the impurity is shown in the Table to be 0.11 area % (GC).
• the basic is experiment is as follows: 5 grams of activated molecular sieve were put into a 40 cc cylinder. An amount (5, 10 or 20 grams) of the crude mixture (which also contains cis HFO-1234ze and HFC-245fa) was put into the cylinder containing the sieves. The cylinder was then allowed to sit at room temperature (23° C.) overnight. The gas was then removed from the cylinder using liquid nitrogen on the receiving cylinder and very gentle heating on the cylinder with the sieves. The gas was then analyzed for the undesirable HFO-1234 impurity. When the molecular sieve was 5 A, there was no undesirable HFO-1234 impurity detected. When the molecular sieve was 13X, some of the HFO-1234 impurity was still present.

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• 2011
  • 2011-04-20 US US13/090,550 patent/US8337595B2/en not_active Expired - Fee Related
• 2012
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